Telescopic jack structure



Dec. 12, 1944. D. R. MERCHANT 2,364,741

TELESCOPIC JACK STRUCTURE Filed Nov. 26, 1942 2 Sheets-Sheet l DONALD l2. Magma,

:Ei i I $314 may;

Filed Nov. '26, 1942 2 Sheets-Sheet 2 Patented Dec. 12, 1944 TELESCOPIC JACK STRUCTURE Donald R. Merchant, Minneapolis, Minn., assignor to St. Paul Hydraulic Hoist Company, Minneapolis, Minn., a corporation of Michigan Application November 26,1942; Serial No. 466 999- 2 Claims.

My invention relates generally to improvements in telescopic jacks or hoists.

Such structures, usually hydraulically powered, are used in many fields for lifting loads of various kinds, elevating the bodies of dump trucks, and for pushing heavy objects. The telescopic version of such devices-is made of a number of short, telescopically assembled sections, or piss tons, so that when collapsed the jack is comparatively short, but so that a long working stroke will be obtained when the sections are extended, this being a very desirable feature in many instances. However, the packing or sealing around the sliding, telescopic sections to prevent the escape of fluid has long been a problem, particularly since such packing, being required around each section, is quite expensive and its frequent replacement has represented quite a service expense.

It is the primary object of my invention therefore to so improve the telescopic jack or hoist structure that no expensive and troublesome packing is required at all to thus provide long, trouble free life for the jack.

Another object is to provide a jack of this nature in which the chief fluid sealing means between sections takes the form of ordinary piston rings in order to take advantage of their efiicient and long wearing qualities, but in which provision is furthermore made to take. care of fluid leakage past the rings, without interference with the operation of the jack, to thus compensate to enlarge degree for normal wear on the rings and add to the useful life of the jack before it requires overhauling. Still a further object is to provide such a jack structure in which the fluid escaping pastthe rings is accumulated and returned to source without loss and in which the requisite auxiliary sealing and wiping of the jack sections in their extended positions is provided by simple, inexpensive and practical means.

These and other more detailed and specific objects will be disclosed in the course of the following specification, reference being had to the accompanying drawings, in which Fig. 1 is a View, partially in diametrical section and partially in side elevation, of a jack structure embodying my invention, the telescopic sections thereof being shown as partially extended.

Fig. 2 is across section taken substantially along the line 2-2 in Fig. 1. Fig. 3 is an enlarged fragmentary sectional view through an end portion of the innermost telescopic jack section showing the return check valve therein inits closed condition.

Fig. 4 is 'an enlarged section along the lined-4 in Fig. 1 but showing the jackin collapsed or retracted condition.

Referring now more particularlyand by refer 'ence characters to the drawings, thejack or hoist structure as disclosed therein is seen to comprise five sections designated generally at 5, 6,1, Band 9- which are telescopically arranged coaxially about anaxis herein illustrated and described as vertical, although it is to be understood that the jack may bearranged and operated in any necessary position.

The'outer or outside section 5, which may be considered as the main cylinder or housing for the jack hasa base flange l0 on-itslower end by which it is secured byscrews II to a base l2. of any suitable form which serves as: a support or mounting for the jack and which. has an. inlet chamber I3. communicating with the open. lower end of said outer section Fluid is admitted to thischamber'through a connection [4 piped. to the Usual pump, valve and. reservoir assembly (not shown) so thatfluidmay be. admitted under pressure to the jack, orreturned to thereservoir;

Said outer section Shas a cylindrical. barrel. or wall provided near its upper end with an opening 15 of relatively reduced diameter, the wall near this open. upper end being, accordingly thicker than-it is below. The next adjacent inner section 6. is similarly formedwith'a reduced upper end opening 16 and at its lower end portion is diametrically enlarged. to form an enlarged end or tail. portion I! nicely and slidably fitting the interior of the barrel of the-outer section 5. The succeeding inner sections 1 and 8- are similarly formed with reduced upper end-openings I8 and [Sand diametrically enlarged lower ends 20- and 2.1, respectively. The innermost or inside section, or. plunger 9, is however closed at its upper end as indicated at 22 but has a diametrically enlarged lower end portion 23 fitting the interior of theibarrel of the next to insideisection 8. The upper. end closure 22 supports a pedestal 24 or other device which is connected to or braced .against the work. to be used. The sections of course grow progressively smaller in diameter from the outermost to: the innermost, as clearly shown.

It will be noted that the foregoing structure and assembly is such that each section maybe moved outward or upward axially within and with respect to the next outer one, such movement being limited by the engagement of the f enlarged ends. of each section with the reduced upper end openings of the next. When collapsed the sections are all substantiallyenclosed within the outermost one 5, although each section extends at its upper or outer end beyond the corresponding end of the next outer section by a short distance.

The inner or lower ends of the inside and intermediate sections 3, l, 8 and 9 are partially closed by end plates or disks designated at 25, 26, 2? and 28 respectively and each of which has a central port or opening 29. In addition the end lates 25, 26 and 21 facing coresponding ends of successive inner sections are circularly recessed on upper faces as indicated at 3B. These end plates will of course limit downward or collapsing movements of the various sections (Fig. 4) while such movement of the next to outermost section is limited by contact with shoulder portions 3| of the base i2 shown in Fig. 1.

In the operation of the structure as thus far described it will be evident that as fluid is admitted under pressure to the chamber l3 its force exerted on the exposed end 25 of the large section 5 will move this section outward (Fig. 1) until such movement is stopped as previously described. The fluid will also flow through the openings 29 in the ends 25, 26 and 21 and into the recesses 30 coming to bear then upon the ends of the next inner sections causing their extension in sequence. The opening in the end 28 of the innermost section or plunger 9 is closed to fluid pressure by a check valve device 32 so that this section also will be forced upward or extended. The sections will move one at a time, with the largest one moving first due to its greater effec tive area exposed to the fluid pressure in the usual manner in such devices. When the pressure is relieved'the sections will close or contract in the inverse order with the displaced fluid returning to the reservoir.

. The outer surfaces of the moving sections are kept clear of dust and the like by wiper rings 33 of leather or similar material secured to the upper or outer ends of all :but the innermost section. Metal bands or rings 34 are pressed down- 35, as shown. g

It will be noted that the reduction in diameter of the open upper ends and opposite enlargement of the lower ends the sections has, the effect of forming between the barrels of the re:- spective adjacent sections the annular chambers designated at 36, 31 and 33 and 39. The fluid exerting pressure on the ends of the sections of course will have a tendency to pass between the sliding surfaces of the barrels and enlarged section ends and thus enter these chambers, and this tendency is largely counteracted in any structure by providing each enlarged section end ll, 20, 2| and 23 with several piston rings, designated throughout at 40, received in grooves 4i. These rings when new and properly fitted will thus serve to prevent the escape of fluid but should such fluid leak past the rings it is permitted to enter the chambers by providing each section above the rings, with a'reduced portion 42 and notches 42 leading from the uppermost rings to the chambers. Also above the rings each section (except the outermost or cylinder section of course) has an annular grove 43 into which said notches 42 and said reduced ortion 42 open and each of these sections further has a series of radially extending ports or channels 44 opening at one end into the groove 43 and at inner ends opening into the interior of the sec- 45 wardly on the wipers and held thereon by screws tions. Said ports are further angled so that in the resting or collapsed position of the jack sections each port will open also into the groove 43 of the next inner section as seen in Figs. 1 and 4. The ports in the innermost or plunger section 9 need not incline in this manner since it opens straight into the hollow interior or accumulating chamber 45 of said section.

Arranged within all but the inner section are the sealing rings 45 of treated leather or other suitable material, such rings being located below the shoulders 41 formed at the reduced end opening l5, it, l8 and IQ of the respective sections in grooves 48 formed for their reception. The rings 46 are thus positioned so as to be contacted by the enlarged ends of each adjacent inner section as the jack expands as shown in Fig. 1.

A relief or air breathing passage 49 is formed in the closed upper end 22 of the inner or plunger section 9 leading from the chamber 45 therein to the atmosphere.

The check valve 32 as shown includes a housing 50 screwed in the opening 29 in the plunger 28, which opening is tapped for this purpose, and this housing has a chamber 5| opening interiorly into the plunger section 9, through a small opening 52. A valve ball 53 is placed in the chamber 5| and retained against downward displacement by a diametrically extending retainer pin 54, the ball normally of its own weight resting on the pin (Fig. 4) and permitting fluid passage through the opening 52. However when fluid pressure is exerted upwardly, as in actuating the jack, the ball is caused to seat in and close the opening 52 (Fig. 3) to isolate the fluid pressure from the interior of plunger section 9 as previously mentioned. Obviously aflap check valve might be substituted for the ball check herein shown and a spring might be arranged to open the valve should the jack be used in such position that gravitywould not sufiice for this operation.

In operation now should fluid leak past the rings 49, as it will in time, it will enter the various chambers 36 through 39 but as the jack is extended any oil in these chambers may escape through the notches 42, grooves 43 and ports 44 and enter the inner or accumulating chamber 45. Thus as the outer section 6 is first extended, the trapped fluid in chamber 36 will pass through the four ports 44 into chamber 45 and as each successive section extends the .same action will take place, it being understood that the ports 44 will always so register with the grooves 43 that passageway will be provided from the closing chambers 35, 31, 38 or 39 into chamber 45. As the fluid accumulates in chamber. 45 it I may escape back to source or reservoir through the valve 32 which opens when the jack is collapsed or at rest. The breather passage 49 of course provides for the necessary air displacement as the chamber 45 receives, the fluid, and permits air to enter as fluid returns to its source through check valve 32 preventing the formation of a' prevent any fluid escape when the jack is extended.

Ordinarily jacks or hoists of this kind have no sealing means whatever at lower ends of the sections and in lieu of the rings 46 in my structure have elaborate glands or packings which bear the full responsibility of preventing pressure and fluid loss. Such packings are necessarily fairly complex and expensive and being subject to much wear and full fluid pressure require frequent replacement.

In my structure however I provide piston rings as the main sealing means, provide for the accumulation of fluid which may pass the rings and return to source, and finally provide as auxiliary sealing means the simple rings 46 which however are greatly increased in eflectiveness by the fact that the pressure of the fluid, against the sections, is employed to compress the rings and increase their effectiveness. Obviously the piston rings ll] will give long Wear as will also,

the rings 46 when used in my structure.

It is understood that suitable modifications may be made in the structure as disclosed, provided such modifications come within the spirit and scope of the appended claims. Having now therefore fully illustrated and described my invention, what I claim to be new and desire to protect by Letters Patent is:

l. A hydraulic jack structure of the character described comprising an outer cylinder section and an inside section telescopically mounted therein and having an end arranged for fluctuation by fluid pressure to extend said inside section endwise relative to said cylinder section, the said sections being formed with an annular chamber between their walls, piston rings arranged adjacent said end of the inside section to normally prevent the leakage of fluid into said chamber, the said inside section having a circumferential groove communicating with the outer piston ring and means communicating'between the groove and said chamber, and the saidinside section also having an interior chamber and port means through its Walls communicating with the groove and adapted to conduct fluid therefrom to the interior chamber'of the inside section.

2. In a hydraulic jack structure, an outside cylinder section, an inside plunger section and a plurality of intermediate sections therebetween, all of said inside and intermediate sections being telescopicallymounted one within the other and Within the outside section for endwise extension toward one end in response to the pressure of fluid exerted on their other ends, each of the intermediate and inside sections having enlarged ends slidably engaging the interior surfaces of adjacent outer sections and forming annular chambers for the reception of fluid leaking past the said enlarged ends, the said intermediate sections having grooves communicating with the annular chambers and having ports leading inwardly from each of said grooves and normally registering with the grooves on the next inner sections but movable out of registry with these grooves as the sections are fully extended, said inside section having an interior accumulating chamber, and means for leading the fluid from said grooves and ports in the intermediate sections into said accumulating chamber.

DONALD R. MERCHANT. 

